Earlier attempts at complete automation of industrial type molded case circuit breakers have not heretofore been feasibly successful. One of the problems interfering with the robotic assembly of the circuit breaker components is the attachment of the movable contact arm or carrier and contact spring to the crossbar assembly. The robotic assembly of the circuit breaker components can be greatly simplified by preassembling the carrier and contact spring to the crossbar prior to insertion within the circuit breaker case. One difficulty that occurs when assembling the contact spring to the crossbar, however, is the "loading" of the contact spring to bias the carrier in a set position relative to the crossbar. "Preloading" the contact spring in a simplified manner would beneficially allow robotic assembly of the crossbar assembly within the circuit breaker case. One purpose of the instant invention, therefore, is to provide a crossbar assembly containing a preloaded contact spring which can be completely pre-assembled by automated means prior to insertion within the circuit breaker case.